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Discussion Starter #1 (Edited)
There's a leak in the fuel lines at the tank. I'm including a pic. Just feeling at the connections the one absent a valve shows fuel at the joint where the hose connects to the fitting. I'm not 100% but this looks like the return. The problem I'm having is that its hard to start when cold. Would a leak on the return side cause this? What's the fix?

 

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That should not affect starting in any way. If it was the main fuel line you would have all kinds of engine issues and not just hard starting when cold.
 

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Especially a diesel engine .... because if you have leak in the suction line you will get air into the fuel system and nothing causes more weird issues on a diesel than a tiny bit of air. If you get a lot of air into the fuel then it just won't run at all.
 

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Discussion Starter #5
Hmm.. That's not contradictory? I think it gets just a bit if air on the suction side and won't start until its been cleared, which is why its hard to start but runs fine otherwise. Especially if its the return line depressurizing the entire system as it sits, because then once the engine runs there's no more air getting in, only exiting on the low pressure side. At least this is my thought. I'm just wondering if the leak on the return side can cause air to get into other parts of the system and cause my starting problem.

Also I'm wondering about the fix - there aren't clamps on the line, I assume they must not be appropriate? What will need to be done to seal the leak? I think it should be fixed regardless of whether its causing my starting problems right?
 

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Hmm.. That's not contradictory? I think it gets just a bit if air on the suction side and won't start until its been cleared, which is why its hard to start but runs fine otherwise. Especially if its the return line depressurizing the entire system as it sits, because then once the engine runs there's no more air getting in, only exiting on the low pressure side. At least this is my thought. I'm just wondering if the leak on the return side can cause air to get into other parts of the system and cause my starting problem.

Also I'm wondering about the fix - there aren't clamps on the line, I assume they must not be appropriate? What will need to be done to seal the leak? I think it should be fixed regardless of whether its causing my starting problems right?
Nothing contradictory there.
The return line usually is the bleed from the injectors and you can do anything you want with that - you could run it into an open bucket and it won't make a difference. Even if it didn't leak, that line just goes into the top of the tank which is vented anyway.
The fitting is one you see in autonotive stores. I don't know how they seal. Are you sure it's the hose-to-fitting and not the fitting-to-right angle fitting ?
Yes, it should be fixed no matter what but it ain't causing your hard starting issue!
 

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Discussion Starter #7
Especially a diesel engine .... because if you have leak in the suction line you will get air into the fuel system and nothing causes more weird issues on a diesel than a tiny bit of air. If you get a lot of air into the fuel then it just won't run at all.
Exactly. When I bought the boat I couldn't get the engine to run at all. I bled the lines and presto! Fired right up. I'm sure there could be a leak in the system elsewhere as well causing the problem, but I'm 99% certain this is what it is. A little bit of air in the line is making the engine do weird things, right?

What else should I be looking for that's causing the hard starting?
 

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What else should I be looking for that's causing the hard starting?
There are many many possibilities but assuming the engine starts up quickly when warm, even after having been stopped for an hour, I would look at the glow plugs. How long do you activate the glow plugs for before attempting a cold start?
Is the engine turning over quickly during the start or is it slow and obviously labouring?

Beyond those basics we could be talking low compression, fouled injectors and a host of other possiilities. Unfortunately those are a bit more difficult to diagnose via internet.
If you suspect air getting into the fuel system, that is a possibility too but it would not relate to the fuel return system.

BTW, if you are doing excessive cranking trying to start the engine, watch that you you don't fill the water lift muffler with water - you could cause a water lock situation and all kinds of damage.
 

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What kind of engine do you have? As posted earlier a leak in the return shouldn't affect your starting.

Older Yanmars for instance, if it's cold, want the throttle advanced when starting. Remeber you can't 'flood' a diesel, just be ready to throttle back to idle when she starts.

If you have glow plugs I'd be checking that next.
 
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